These days, the importance of water has been spotlighted to the point where water is the most important factor of the secret of longevity, and as a result, public interest in water has increased. Various waters such as the water in predetermined areas, deep ocean water, oxygen-rich water, alkaline water, and the like have been gradually commercialized and sold. Interest in the oxygen-rich water among various kinds of waters has also increased and an attempt to a method for efficiently producing the oxygen-rich water has been made.
In one of known methods for increasing dissolved oxygen in water, while water and oxygen are charged in an airtight container and pressurized, water and oxygen were left for a long time to dissolve the oxygen. However, since a sturdy tank, a high-lift valve pump, and a high-pressure oxygen tank are required to implement this method, the volume and weight of a system increase and a unit production cost of oxygen-rich water increases. Therefore, when oxygen is dissolved in drinking water in a small-scale apparatus such as a water purifying filter or an oxygen-rich water generator, this method cannot be applied due to the volume and weight, a production cost, and the like.
Further, one of method for dissolving oxygen in water increases a contact area between oxygen and water by consecutively inputting gas with sufficient oxygen into water. Dissolution efficiency is low to dissolve oxygen approximately at saturation concentration in this method, but this method cannot be applied to an application field requiring supersaturation.